A communication network may include network elements that route datagrams (e.g., frames, packets) through the network. Some network elements may include a distributed architecture, wherein datagram processing may be distributed among several subsystems of the network element (e.g., line cards, switches, and traffic managers).
In many instances, communication networks may employ link aggregation. Link aggregation (e.g., IEEE 802.1AX-2008) may generally describe the practice of using multiple network cables or ports in parallel to increase the link speed beyond the limits of any one single cable or port. Link aggregation may also be used to provide fault protection by increasing redundancy for higher availability. In link aggregation, a group or set of ports may be combined and represented as a single logical port to other components of the network system. Various switching elements of the network system may “see” the aggregated ports (known as a “link aggregation group” or “LAG”) as a single logical communication port in the routing tables or databases of network elements external to the LAG.
In addition, to ensure high reliability and availability in communications networks, protection switching is often used. When implemented, protection switching typically provides a primary or “working” path for a network and a redundant or “protection” path for the network. Accordingly, each path of a protection group may be monitored, and if a failure is detected on the working path, network traffic may be switched to the protection path. A LAG, because it includes a group of ports, may be used to perform protection switching, and is so often used to provide protection for Ethernet interfaces. Other protection schemes in communications networks include unidirectional path-switched ring (UPSR), birectional path-switched ring (BPSR), automatic protection switching (APS), or others.
A particular communication network may include a plurality of network elements for carrying Ethernet traffic between two or more clients via a synchronous optical network (SONET). FIG. 1 depicts an example of a traditional implementation of such a communication network 1. As shown in FIG. 1, communication network may include a plurality of network elements 2, each network element 2 providing an adaptation layer interface 110a between Ethernet client interfaces 7 and SONET ports 6. SONET ports 6 may be coupled to a protected SONET network 3. Generally speaking, a network element 2 may perform datagram segmentation, reassembly, and other tasks in order to convert Ethernet packets received at an Ethernet client interface 7 to SONET frames for communication via protected SONET network 3, and vice versa. As depicted in FIG. 1, a network element 2 may include a plurality of plug-in units (PIUs) 4. A PIU 4 may have plug-in terminals so that some or all electrical and/or optical connections of the PIU 4 can be made engaging the unit with a suitable socket of network element 2, and may generally be configured to forward datagrams between Ethernet client interface 7 and protected SONET network 3. In some embodiments, a PIU 4 may be configured to perform datagram segmentation, reassembly, and other tasks in order to convert Ethernet packets received at an Ethernet client interface 7 to SONET frames for communication via protected SONET network 3, and vice versa. A PIU 4 may include a port 5 configured to serve as a physical interface between its associated PIU 4 and Ethernet client interface 7. Similarly, a PIU 4 having a port 5 may be configured to serve as a physical interface between its associated network element 2 and protected SONET network 3.
In traditional implementation such as those depicted in FIG. 1, Ethernet client interfaces 7 may be protected (e.g., enabled for redundancy in the event of failure) using link aggregation and ports 5 comprising an Ethernet client interface 7 may comprise members of a link aggregation group 6. In addition, protected SONET network 3 may be protecting using UPSR, BPSR, APS, or any other suitable protection scheme. However, as seen in FIG. 1, adaptation layer interface 110a may comprise a single point of failure (e.g., by way of a failure of a PIU 4), thus preventing end-to-end protection in network 1. Traditional solutions to this problem include including a redundant network-side port 5 having another transmission path, ensuring that at least one of the network-side ports 5 has a path to the SONET network 3. However, such a solution results in doubling the bandwidth requirements of a network element.